From the bottom image in this article from september 2016 it can be seen that there was a possible path for Curiosity in the direction of Mount Sharp (Aeolis Mons).

At the end of januari 2018 however Curiosity's course was diverted to the left along the hematite-rich Vera Rubin Ridge, indicated as the "haematite unit" on the image.
Since then Curiosity has travelled northeast along the ridge but it will have to descend on the "clay unit" eventually in order to travel toward Mount Sharp.

Clays are important for life because, in addition to being capable to hold water, they contain minerals that may have key elements like potassium and magnesium.

The question now is if Curiosity is allowed to take samples from the subsurface of this clay-rich region to investigate, since water may be present that could be contaminated.
(see this article)